Whether you've decided to move your website to a new domain or you're moving content within a current website, it's important to know how to protect the trust value your current content has with the engines. Over time, links get built, content ages and acquires trust. You don't want to walk away from that if you can help it. Why start over when most of that value can be transferred to the content's new location?
The solution to your problem is the 301 redirect. This redirect is referred to as the "permanent" redirect. Its cousin, the 302 redirect, is the "temporary" redirect. Basically the 301 tells us to please follow the link to find the new home for the content. The 302 on the other hand, tells us the content has moved temporarily, but will return to its original location. Since, in this example, we know you've moved the content permanently, the 301 is the redirect you should use. We've covered this in more detail in a past post.
One big questions folks often have at this point is how much of the value is passed to the new URL. A valid question, and one with a simple answer. Most of the value is passed.
We cannot pass all of the value because, like it or not, that new URL is, well, ...new. We do still need to see many of the usual signals firing to help us close the gap back to the original, full trust value for the content. So, as you watch your stats, you will see a drop in the traffic graph as you work through a transition period. There's no hard and fast rule on how long this transition period lasts, but it usually measured in months or less.
This past week at a conference someone had a question and asked if they could use a rel=canonical in place of a 301. They argued that since the rel=canonical passes value similarly to a 301, it should do the trick.
The answer to the question is...no. You should not use a rel=canonical in place of a 301 redirect. The rel=canonical is designed to help manage duplicate URL issues. It is not a true 301 signal to the engines, though it can pass value similar to the way a 301 does. Implementing a 301 redirect is tough to mess up. It either works or it does not, and when it does, it passes value. We recently encountered a website that had so botched implementing its rel=canonicals that it essentially would lead to all of their pages, save one, being stripped of value and de-indexed over time.
Luckily they've found and fixed the issue, but the fact remains. If you need to move content, the 301 is your friend.